A man dressed in a well-cut but nondescript suit showed up in the office on Monday and offered his services as an anonymous source. For 20 years, he said, he had worked at writing novels. None of his books had sold more than a few thousand copies, and he was sick of playing the toady to publishers and literary critics.

The occupation of anonymous source occurred to him when, in a season of depression, he got into the habit of reading the newspapers. He noticed that the more imaginative plots and the better dialogue often originated with unknown sources variously identified as "informed," "confidential," "Washington," "high level," "White House" and "well placed." Further study persuaded him that the masks served as a disguise for corporate or government bureaucrats with a grievance or a policy.

"Here is a cast of characters easily understood," he said. "The people in my own novels always has a talent for jealousy, envy and secret ambition. All I had to do was to assign them an office in the Pentagon, the SEC or a New York bank. I didn't even have to give them a name."

First he made himself familiar with the statistical jargon and the standard repertoire of simple political issues. For six months he read government budgets, annual reports, congressional testimony, speeches delivered by business statesmen at conventions and sales meetings. Once he had learned what the arguments were likely to be about, the source began to work on the problems of motive and character.

"Confidential information rewards the friends and punishes the enemies of the source," he said. "The question becomes one of giving people reason to hate one another."

Within a year he had developed a plausible technique. He made a few telephone calls to syndicated columnists and staff correspondents at the news magazines. In the beginning, he pretended to be talking from an unspecific crossroads within the interior of an obscure bureaucracy.

"The Department of Agriculture," he said, "is like Namibia. People think they know where it is and what it means. Nobody wants to admit his ignorance of the place."

Pretty soon the source began to see his work in print. In the persona of a White House source, he whispered rumors of Secretary Haig's imperial dream of power, and there they would be in the next day's edition, dressed up in the rubrics of authority, disturbing the peace of nations. As a police informant in New york, the source offered hints about show business celebrities in the maze of sexual illusion; as a specialist in Arab affairs he supplied informatioin about the forthcoming collapse of the oil cartel.

The newspaper clippings he had bound in leather volumes, and these he arranged on the desk as if he were an author exhibiting goods on a talk show. His most recent success he had achieved in Canada. He displayed an article from that morning's paper to the effect that a Canadian newspaper had maligned a minister in the Canadian government. Basing its allegations on confidential information, the paper had accused the minister of corrupt dealing in the stock market, and this in turn had called up a storm of delighted scandal in the Canadian House of Commons.

"You see," said the source, "what can be done."

His sales pitch stressed the simplicity and low cost of operation. Not only would an editor have more control over the news, but the price of the service amounted to a good deal less than the salaries paid to a reporting staff. The source already had signed contracts with various newspaper and television syndicates forced to reduce their editorial budgets.

"Think of it as part of the communications revolutions," he said. "Nobody needs to go anywhere. Every day is Abscam day."

Asked what satisfaction, other than money, he derived from his new occupation, the source looked fondly on the row of his collected works.

"An audience," he said. "I'm writing the great American novel, and they need it in Kansas City and Detroit."

He left a business card with a single telephone number and 17 names, all of them protected by the First Amendment.